Integration of supercapacitors into wirelessly charged biomedical sensors

Conventional implantable sensors are often battery operated. Batteries are characterized by their high energy densities which allow for long term operation. However, it can take a long time to charge up a battery. As an emerging technology, a supercapacitor can be charged very quickly and it is considered as alternative energy storage to replace traditional batteries. This paper proposes an implantable biomedical sensor which operates off a super capacitor which is wirelessly charged. A feasibility analysis of supercapacitors is presented first, and then the system design and implementation are detailed for achieving wireless charging control with digital data logging. Design considerations relating to supercapacitor specific issues are also presented in detail. The implemented circuit can wirelessly charge a 5.5V, 1F supercapacitor in approximately 5 seconds. This capacitor powers a microcontroller and wireless transceiver for approximately 60 minutes before the circuit needs to be charged again.